Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
cua viet » ca viet, hoa viet, cua vat
va thanh » gia thanh, ban thanh, va tinh
vai cua » dai cua, hai cua, lai cua
cac duc » cac du, cao duc, cac dac
sach ty » sach y, sach tu, sach thu
cao hoi » cau hoi, co hoi, cao hoc
cach tu » cach thuc
hieu va » lieu va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ty) or (cach tu)) nang cao hoi. ((hieu va) OR (hieu qua)) cac duc va thanh vai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (cach tu)) nang cao hoi. ((hieu va) OR (hieu qua)) cac duc va thanh vai cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) or (cach tu)) nang cao hoi. ((hieu va) OR (hieu qua)) cac duc va thanh vai cua viet".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (cach tu)) nang cao hoi. ((hieu va) OR (hieu qua)) cac duc va thanh vai cua viet*.